1. Field of the Invention
The present invention relates generally to cutting machines such as horizontal bandsaw machines having a cutting blade such as a bandsaw blade held in a cutting head assembly to perform cutting operations and, more particularly, pertain to methods and apparatus for controlling the upward or returning movement of the cutting head assembly in cutting machines.
2. Description of the Prior Art
The prior art concerning the present invention will be described, by way of example, about what is called a horizontal bandsaw machine, although the present invention is applicable to a variety of cutting machines such as circular sawing machines.
As is well known, horizontal bandsaw machines comprise a base on which a workpiece or workpieces to be cut are to be placed and clamped and a cutting head assembly in which a flexible endless bandsaw blade is trained around a pair of wheels or pulleys, one of which is power driven to drive the bandsaw blade. In the cutting head assembly, the bandsaw blade is slidably held and guided with its cutting edge faced perpendicularly downwardly by a pair of guide means at the cutting zone where cutting is performed so that it may cut into the workpiece to be cut. The cutting head assembly is so arranged as to be raised away from and lowered toward the base by a suitable means such as a hydraulic motor around a hinge pin or along one or more vertically disposed guide means. Thus, in each cutting cycle, the cutting head assembly is firstly raised and then lowered towards the base so as to enable the bandsaw blade being driven therein around the wheels to cut the workpiece which has been placed and clamped on the base. Also, in automatic horizontal bandsaw machines there are provided arrangements for automatically raising and lowering the cutting head assembly and automatically feeding workpieces to be cut into the cutting zone after completion of each cutting cycle.
In the horizontal bandsaw machine of the above described arrangement, it is desired to minimize the up-and-down movement of the cutting head assembly in order to minimize the idling of the bandsaw blade. In other words, it is required to make the upper or returning limit of the bandsaw blade as low as possible depending upon the height or diameter of the workpiece to be cut. On the other hand, however, it is necessary to make the returning limit of the bandsaw blade a little higher than the top surface of the workpiece to be cut so as to prevent the bandsaw blade from being damaged by the workpiece being fed, since the workpiece is not exactly straight but more or less uneven. Accordingly, in order to minimize the idling of the bandsaw blade, it is further desired to lower the cutting head assembly carrying the bandsaw blade at a faster rate before the bandsaw blade cuts into the workpiece.